1. Field of the Invention
The present invention relates to railway crossing detectors.
2. State of the Art
A conventional railway crossing controller is depicted in FIG. 1. The railway crossing controller maintains control of the signal lights and cross bars at the road crossing the railway tracks. It is activated by an electrical "shunt detection system" located some distance from the crossing. This is an electrical system which detects the closed electrical contact of a train crossing a physical location in the tracks. It is nominally located 3000 feet either side of the crossing.
There are several drawbacks to the conventional shunt system. The first is that it cannot give an indication of the trains direction or speed. This can represent a nuisance factor for slow trains where the shunt would close the crossing gates well before the train reached the crossing, possibly causing impatient motorists to try and cross the track in spite of the fact that a train is approaching. This represents a potentially hazardous situation. The other factor is that shunt systems can be falsely activated by conductive material falling across the tracks. This could occur by natural causes or by acts of vandalism.
The railway crossing detector described herein deals only with the detection system and not the interface to existing crossing controllers.